Anti-aircraft warfare generally involves the launching of rockets or guided missiles that target an aircraft. A guided missile includes a guidance mechanism which directs the missile to lock on to and track a moving target during the missile trajectory (i.e., homing). For example, an infrared homing guided missile, also known as a heat seeking missile, detects the infrared radiation emitted by the target (e.g., the exhaust expelled from the jet engines) to provide guidance. Another type of guidance mechanism is based on radar, in which the missile or a radar ground station transmits radio waves toward the target, and then the missile detects the return signal reflected by the target.
A targeted aircraft may deploy a decoy device to contend with an oncoming guided missile, causing the missile to target the decoy rather than the aircraft. The decoy detects the radar signal transmitted toward the aircraft, and then transmits a decoy signal having the appropriate signal parameters to deceive the missile into identifying the decoy as the intended target (i.e., the aircraft). The missile proceeds to target the decoy, which is eventually destroyed by the missile, while avoiding damage to the aircraft. Such a decoy must contain substantial processing power and capabilities, which adds weight as well as cost, and additional wasted resources once the decoy is destroyed.
It is also possible for the aircraft to detect the signal from the oncoming missile and then to transmit the required data to the decoy. The aircraft may send the decoy operating parameters, such as what type of signal to transmit and in which direction, and may monitor the status of the decoy. The data transmission is generally accomplished with a dedicated data link, such as optical fiber cables connecting the aircraft to the decoy. For example, the decoy may be arranged on a cable drum inside the aircraft, and the cable is released and unraveled outside the aircraft once the decoy is deployed. Such a cable also adds to the overall weight of the aircraft.
The decoy is typically attached to the aircraft, also known as a “towed decoy”. Accordingly, the connecting cable can also be used to transmit data between the aircraft and the decoy. If the decoy is detached from the aircraft, the aircraft must transmit data using a wireless communication link. Alternatively, the aircraft may transmit the required data to the decoy prior to deployment, while the decoy is still onboard the aircraft.
A particular problem arises due to the fact that the decoy signal transmitted by the decoy is at a similar frequency to the radar signal detected by the decoy from the missile. The decoy may detect its own transmitted signal and mistakenly consider it to be the radar signal from the missile, resulting in a continuous feedback loop. Similarly, if the aircraft is operative to detect the radar signal and to communicate this information to the decoy, the aircraft may detect the decoy signal transmitted by the decoy and mistakenly consider it to be the radar signal from the missile.
U.S. Pat. No. 7,142,148 to Eneroth, entitled “Towed decoy and method of improving the same”, is directed to a towed decoy arrangement for an aircraft having a towed decoy. The aircraft includes a receiving antenna, a transmitting antenna and an analysis and noise signal generating device, which may include the aircraft jamming equipment. The receiving antenna detects a threatening signal from a threat source (e.g., a missile or homing device), and the analysis and noise signal generating device generates a noise signal, which is transformed to a higher frequency that is rapidly attenuated through air. The transmitting antenna transmits the transformed noise signal to the decoy. The frequency of the transformed noise signal is generally higher than 58 GHz, and in particular, at about 77 GHz with a 10 GHz bandwidth. The decoy includes a receiving antenna, means for signal transformation, and a transmitter with a transmitting antenna. The decoy receiving antenna receives the transformed noise signal from the aircraft, and converts the received signal back to a noise signal, by shifting the received signal to the frequency of the threatening signal and amplifying it. The decoy transmitter then transmits the noise signal in the direction of the threat source.
U.S. Pat. No. 6,804,495 to Duthie, entitled “Wireless communicator link from towed/surrogate decoy transmitter to the host aircraft”, is directed to a method of communication between a towed decoy transmitter and the host aircraft using a two-way wireless communication link. Both the host aircraft and the towed decoy include an RF wireless transceiver connected via the wireless link. The host aircraft transmits a host RF drive signal through the tow cable (e.g., using fiber optics, modems or coaxial cables) to the decoy. The decoy transmitter transmits an RF electronic countermeasure (ECM) output signal in fore and aft directions, such that an RF based tracking missile will lock on to the decoy rather than the aircraft. Operational control signals, such as to modify performance parameters in the decoy, are transmitted from the host aircraft wireless transceiver to the towed decoy wireless transceiver through the wireless link. The operational control of the decoy can then send an operational adjust signal to the transmitter to modify the relevant parameters. Built-in-test (BIT) circuitry in the decoy monitors performance specifications of the decoy transmitter, and this information can be transmitted as a BIT data signal to the host aircraft wireless transceiver from the towed decoy wireless transceiver. The host aircraft operational controller can then send back commands to adjust or check a performance parameter, or display the information to the pilot. The operational performance information may be communicated through the existing on-board RF ECM antenna on the host aircraft and decoy antenna on the decoy, if available, rather than through the wireless communication link. In circumstances with multiple host aircrafts and decoys, each host aircraft or decoy may transmit or receive data from another host aircraft or decoy. For example, a master host aircraft responsible for overall deployment strategy can control the RF ECM signal of any decoy.
UK Patent No. GB 2,303,755 to Morand, entitled “Electronic counter-measures for towing by an aircraft”, is directed to an ECM device for an aircraft, which includes a towed auxiliary device that can be deployed from the aircraft during flight. The auxiliary device is connected to the aircraft with a towing cable. A primary receiver on the aircraft detects incident radioelectric signals relating to a threat, and a generator circuit produces a jamming signal and digital commands. A power supply on the aircraft produces a high voltage, high frequency power current. The jamming signal is transmitted to the auxiliary device via optical fibres arranged around the towing cable, and the logic signals and feed current are transmitted over bifilar metallic links. The feed current powers all the internal circuits of the auxiliary device. The jamming signal is applied to a preamplifier and correcting device, followed by a transmitting amplifier, and an ultra high frequency commutator. The commutator directs transmission of the jamming signal from either a front antenna or a rear antenna, arranged respectively under radomes at the front and back of the auxiliary device. The commutator is controlled by the received logic signals, in accordance with whether the threat is in front of or behind the auxiliary device. The jamming signal may be transmitted over a single optical fibre in a spectral band between 6-18 GHz using a single laser transmission diode. Alternatively, the signal may be transmitted over two optical fibres in two separate frequencies, and recombined at the auxiliary device.